Thiocyanate ammonium additives are found to improve the performance of FAPbI 3 based planar perovskite solar cells through a single one-step method.
Thiocyanate ammonium (NH 4SCN) is introduced into the fabrication of formamidinium lead triiodide (FAPbI 3) films through one-step spin-coating. The promoted formation of black trigonal phase α-FAPbI 3 with better crystallinity has been observed after the addition of NH 4SCN, together with the supression of the formation of yellow hexagonal phase δ-FAPbI 3. Planar perovskite solar cells (PVSCs) based on NH 4SCN-assisted formed α-FAPbI 3 films with high quality present a highest power conversion efficiency of 11.44% when 30 mol% NH 4SCN is applied. Notably, the addition of NH 4SCN is found to enhance the moisture stability of the perovskite. As a result, the planar PVSCs with 30 mol% NH 4SCN additive show improved stability under ambient conditions (RH: 30–40%) over those based on pristine FAPbI 3. NH 4SCN simultaneously enhances the efficiency and moisture stability of FAPbI 3 based PVSCs through a single one-step solution method, facilitating their commercial fabrication and application.